Wide mouth plastic containers for hot ingredients, in particular containers made of polyethylene terephthalate (PET), are commercially available. These PET containers typically are formed from a wide mouth preform using conventional blow molding techniques. The wide mouth container formed by such a the conventional blow molding process, results in a container having a neck of insufficient strength and thickness in comparison with the rest of the container. This is because with conventional blow molding techniques preforms that have threads already formed in the preform are used. In such preforms, if they are to be utilized substantially in their entirety, as is now customary in bottle forming, the diameters of the mouth of the preform must match that of the resultant container and the blow molding of the preform will result in insufficient biaxial orientation of the container particularly in the container body wall adjacent the open mouth.
A heat setting process helps to alleviate potential shrinkage and distortion, however, the finish of a conventionally blown wide mouth container is not exposed to this heat setting process.
It has also been proposed (U.S. Pat. No. 4,576,843) to create a wide mouth container using a preform with a small diameter preform as is customarily utilized in the blow molding of bottles with the preform being of a materially lesser length than that of the resultant container. Here there is formed an intermediate article of manufacture which has a portion in the form of an accommodation element which permits the necessary biaxial orientation of the thermoplastic material throughout the container, the accommodation element being severed from the container and becoming reusable scrap. This technology results in preforms having a flanged portion where the resultant trimming typically takes place. The trimming results in a wide mouth container biaxially oriented throughout with a flange as its neck portion. This flange is used to attach a lid for holding the contents within the container. The present technology does not provide a hot fillable wide mouth container which resists shrinkage and distortion at hot fill temperatures greater than 160.degree. F.
An object of this invention is to provide a wide mouth container blow molded from a small diameter preform (as opposed to a parison used in extrusion blow molding), as is customarily utilized in the stretch blow molding of bottles, wherein the entire container, including the neck finish, is biaxially oriented and heat set to give thermal stability to the entire container.
Another object is to provide a method of post forming (i.e. post formation of the container by blow molding) neck finish features of the container.
Another object is to provide a wide mouth container having a screw thread formed during the blowing operation.
Another object is to increase the geometric strength of the container by curling the edges of the finished container, so that the container is better able to withstand distortion and shrinkage. This acts as a safety lip for drinking from the container and a means of providing a "snap" cap when made without blown threads.